The production of nonwoven fabrics, fleeces and mats from thermoplastic synthetic resin filaments, hereinafter referred to as webs and especially spun-bond webs, is known. The filaments, usually endless filaments, i.e. filaments which theoretically can be continuous and are thus distinguishable from so-called staple fibers which are relatively short threads, can be collected on a surface and accumulated in a jumble or random collection of the filaments so as to produce the nonwoven web. The web itself can be fabricated in a continuous manner and the product, when composed of continuous filaments, filaments which are not intentionally broken up or filaments which can be theoretically continuous and thus as long as possible without interruption in the extrusion of the filaments from a spinneret, is known as spun bond.
The filaments collecting upon a surface tend to bond together at crossover points. The surface upon which the filaments collect can be a moving surface, preferably the surface of an endless belt which circulates below a curtain of the filaments descending from a spinneret. The filaments can be aerodynamically stretched between the spinneret and the collecting surface.
The formation of hydrodynamically consolidated spun-bond webs from filaments or endless strands can be contrasted with the formation of nonwoven webs from shorter fibers in the so-called melt-blown process. In the melt-blown process, the strands emerging from the spinneret are broken off to stable fibers and the fiber is collected on a surface. The melt-blown product has a significantly smaller amount of looping of the strands.
The spun-bond webs which have been produced heretofore have somewhat lesser degrees of a fleece characteristic than the melt blown webs and may have a lesser strength, especially because of a somewhat smaller degree of consolidation. Furthermore, spun-bond webs can show a greater tendency toward abrasion wear than is desirable. Attempts to avoid these drawbacks have led to the development of intensive hydrodynamic consolidation of the web in the case of spun bond which, in turn, leads to greater cost, especially in terms of the cost of energy used in the fabrication process and may contribute to limited production speed.